World's Biggest Virus Identified
Remedies for lung, eye, brain, and heart problems
THIS ONE'S BIG
PARIS
French researchers say they have uncovered the world's largest known virus, a pneumonia-causing agent found in amoeba that lurk in air-conditioning systems, but stress it has no link with the respiratory epidemic that had broken out in Asia. The virus is so big that it was at first mistaken for a bacterium and is visible through a good optical telescope, usually impossible for viruses, they say.
It has been dubbed Mimivirus, short for "mimicking microbe." So far, nearly 900 genes have been identified in its genome, an enormous figure for viruses.
"It is a potential agent for pneumonia," one of the researchers, Didier Raoult of the National Center for Scientific Research (CNRS), said. "Blood samples of people with pneumonia have revealed antibodies for this virus," he said.
Mimivirus has now been categorized as the first in the new Mimiviradae virus family, although it shares some genetic ancestry with the pox viruses. Its length is about 800,000 base pairs, which compares with 670,000 base pairs for the previous record-holder, Bacillus megaterium.
The initial Mimivirus sample was taken by a British microbiologist, Tom Rowbotham, in the cooling tower of an air-conditioning unit in Bradford, northern England in 1992.
PROTECTIVE PATCH
SYDNEY
Vital Health Sciences, an Australian company, said it was developing a skin patch that could protect wearers from attacks with nerve gas and other deadly gases. The patch would deliver chemical agents including deadly sarin, tabun, and soman gases.
Atropine is currently only administered through intramuscular injection, which must be repeated every 20 to 30 minutes while the poison is present in the atmosphere. Esra Ogru, research manager for the company, said an initial atropine injection would still be necessary after chemical exposure, but the patch could be used afterwards in place of repeated injections.
CLOSING IN ON EMPHYSEMA
PARIS
Genetic detectives believe they have identified a group of genes that may make an individual susceptible to emphysema.
University of California scientist David Morris and colleagues say they have traced the path that leads to Mmp12, a gene that has long been fingered in emphysema. Mmp12 produces an enzyme that destroys elastin, the protein that helps to keep lung tissue elastic, like a pair of bellows.
The Morris team followed the genetic path to look for the events that triggered Mmp12, according to their research, published in Nature. A series of other genes are involved in activating Mmp12, notably one that controls a protein called TGF-B (transforming growth factor-beta), they say.
The genes were identified in mice that were genetically modified to replicate emphysema symptoms, but the authors are confident that the same genes exist in humans. If so, that opens up exciting avenues for diagnostic tools to identify people at risk for emphysema and for treatments to prevent the disease, said Anita Roberts, an expert in cell regulation at the US National Cancer Institute.
"Emphysema is predicted to become one of the top five causes of death and disability worldwide by 2020," she said. The biggest cause is smoking, but only 15 to 20 percent of smokers develop emphysema, suggesting possible genetic disposition, she said.
ORAL TO VISUAL
TOKYO
A team led by a Japanese eye doctor has succeeded in restoring the sight of patients by cultivating an artificial cornea out of membranes taken from their mouths.
The team led by Dr. Takahiro Nakamura at the Kyoto Prefectural University of Medicine performed operations on nine patients who had lost their eyesight due to illness or injuries to the surface of the five-layer cornea.
Surgeons removed two-square millimeter membranes from the patients' mouths and cultivated them for three weeks on tissue from the amniotic sac, the membrane which surrounds embryos in the uterus, a report by the Japanese news agency Jiji Press said.
The patients received the graft of the membranes once they grew to three square centimeters. Eight of the nine patients recovered their vision after the operation. One procedure failed due to the effects of another illness.
The new method was presented at a meeting of the Japanese Society for Regenerative Medicine in Kobe.
ARTIFICIAL BRAIN TISSUE
PARIS
US researchers are poised to carry out the first tests of a silicon chip designed to replace a damaged part of the brain. The implant aims to stand in for the hippocampus, part of the forebrain vital for storing long-term memories, according to a report published in New Scientist.
It will shortly be tested on tissue from rats' brains, then on live rats and laboratory monkeys, and if all goes well could one day be used for people who face memory loss due to Alzheimer's disease, epilepsy, or stroke.
The prosthesis mimics the way the hippocampus encodes experiences before sending them to be stored elsewhere in the brain as long-term memories, according to the report.
To make the chip, the team first sliced up sections of rat hippocampus, and stimulated these slices with electrical signals. They did this millions of times over until they could be sure which electrical input produced a corresponding output.
By putting together the information from the various slices, they built up a mathematical model of the entire hippocampus, perceiving it as an array of neural circuits that work in parallel to process data. The model was then transferred onto a chip, which communicates with the brain through two arrays of electrodes, placed on either side of the damaged area. One set of electrodes detects the electrical activity coming in from the rest of the brain. The other sends appropriate electrical instructions back out to the brain.
The chip is the result of a 10-year effort by a team led by Theodore Berger of the University of Southern California in Los Angeles. They are scheduled to put it to the test using slices of rat brain that have been kept alive in cerebrospinal fluid.
If it works, the team will test the prosthesis in live rats within six months, and then in monkeys trained to carry out memory tasks. The researchers will stop part of the monkey's hippocampus from working and bypass it with the programmed chip.
If the invention works and ultimately is proved safe for humans, it would sit on the top of the skull, rather than inside the brain, to reduce damage to cerebral tissue.
FROM ENDING TO SAVING LIVES?
PARIS
American and French researchers say the French-made antiabortion pill is also a potential therapy for treating psychotic depression, a potentially life-threatening illness. RU486 pill dampens surges of cortisol, a stress hormone that has been linked to this form of depression, they report in Biological Psychiatry.
The work was carried out by Etienne-Emile Baulieu, the inventor of RU486, and a team from Stanford University in California. A preliminary trial was carried out on a group of 30 volunteers, men and women aged 25 to 74, who were given doses equal or superior to that used to terminate a pregnancy.
Episodes of psychotic depression cannot be controlled by normal antidepressants, and victims of the condition feel so low that many commit suicide. Baulieu said RU486 "can save lives" in tackling such episodes. "A week's treatment with RU486 helps the patient to overcome the danger, and return to normal medication," he said. But he stressed it was not a therapy for people who suffered chronic manic depression or "reactional" depression to things that went badly wrong in life.
"The role of cortisol secretion in depressions has been studied for more than 20 years... [but] the precise way in which corticoids [adrenal cortex hormones] act on the brain needs further research," he said.
SMALLEST HEART PUMP
SINGAPORE
A Singaporean university has developed a heart pump weighing just 50 grams, which it claims is the smallest in the world.
A key feature of the heart pump developed by the Nanyang Technological University is that it can be used by patients without the need for open-heart surgery, said professor Freddy Boey, member of the research team. The pump has a tiny engine powered by a battery.
"We believe it is the smallest...we have not seen anything smaller than this," Boey said. "The key advantage is you can insert this device without open-heart surgery," he said, adding this meant heart patients could avoid complications like immunological rejections and thrombotic infections.
Boey said the new technology has been licensed to Orqis Medical, a US biomedical company specializing in heart pumps.
HERPES VACCINE
BETHESDA, Maryland
Clinical trials for an experimental vaccine against genital herpes are ongoing in the US in a joint public-private venture. The National Institutes of Health said the prototype for the vaccine, to fight the herpes simplex virus types HSV-1 and HSV-2, will be tested on 7,550 women who are not carriers of the virus, but whose partners are infected.
The trials, which will last 20 months, have been made possible through a partnership between the National Institute of Allergy and Infectious Diseases and pharmaceutical firm GlaxoSmithKline Biologicals based in Belgium.
Previous trials showed 70 percent efficacy in preventing the disease in women. But for reasons not yet known it had no clear effect in men.
"More than one million new cases of genital herpes are diagnosed in the US each year," said institute director Anthony Fauci. "Successful public-private collaborations such as this one will take us closer to our goal of reducing the spread of genital herpes."
Between 50 and 80 percent of the US population are infected with HSV-1, usually during infancy, while one in five people older than 12 have HSV-2.
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